Most mammals depend on their ability localize moving sound, and the echolocating bat is an excellent model system for the study of auditory localization in the presence of motion. Microchiropteran bats use a biological sonar system to navigate through their environment and capture insect prey on the wing. Bats echolocating in flight therefore experience dynamic auditory space both from the stationary environment, and from flying prey. Accurate auditory spatial processing by bats must consequently be carried out in an active environment. Behavioral analysis of the responses to moving sound by the big brown bat, Eptesicus fuscus, is proposed here in an attempt to gain new insight into the mechanisms used to process, utilize, and resist potential localization errors produced by auditory motion. Two sets of experiments are proposed, the first being a determination of head and pinna aim of otherwise stationary bats trained to orient toward moving inanimate targets. The second set of experiments will consist of behavioral analysis of insect captures while the bat is echolocating in flight. The focus of these experiments is to: l) determine the behavioral orienting response of the head and external ears to moving sound, 2) examine how sound motion affects the ability to accurately localize a moving sound, and 3) ascertain the perceptuo-motor strategies used by echolocating bats to intercept moving targets.